<b>HRAC Group 2</b> <font size='2'> (Legacy B) </font> resistant Myosoton aquaticum from China

INTERNATIONAL HERBICIDE-RESISTANT WEED DATABASE

HRAC GROUP 2 (LEGACY B) RESISTANT WATER STARWORT
(Myosoton aquaticum)

Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)

China, Jiangsu, Henan

INTRODUCTION		WATER STARWORT
Water Starwort (Myosoton aquaticum) is a dicot weed in the Caryophyllaceae family. In China this weed first evolved resistance to Group 2 (Legacy B) herbicides in 2010 and infests Winter wheat. Group 2 (Legacy B) herbicides are known as Inhibition of Acetolactate Synthase (Inhibition of Acetolactate Synthase ). Research has shown that these particular biotypes are resistant to tribenuron-methyl and they may be cross-resistant to other Group 2 (Legacy B) herbicides. The 'Group' letters/numbers that you see throughout this web site refer to the classification of herbicides by their site of action. To see a full list of herbicides and HRAC herbicide classifications click here.

QUIK STATS (last updated Apr 08, 2012 )
Common Name	Water Starwort
Species	Myosoton aquaticum
Group	Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)
Herbicides	tribenuron-methyl
Location	China, Jiangsu, Henan
Year	2010
Situation(s)	Winter wheat
Contributors - (Alphabetically)	Weitang Liu, and Jinxin Wang
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ACADEMIC ASPECTS

Confirmation Tests

Greenhouse, and Laboratory trials comparing a known susceptible Water Starwort biotype with this Water Starwort biotype have been used to confirm resistance. For further information on the tests conducted please contact the local weed scientists that provided this information.

Genetics

Genetic studies on HRAC Group 2 resistant Water Starwort indicate that the inheritance is determined by a one gene, dominant trait. There may be a note below or an article discussing the genetics of this biotype in the Fact Sheets and Other Literature

Mechanism of Resistance

Studies on the mechanism of resistance of Group 2 (Legacy B) resistant Water Starwort from China indicate that resistance is due to an altered target site. There may be a note below or an article discussing the mechanism of resistance in the Fact Sheets and Other Literature

Relative Fitness

There is no record of differences in fitness or competitiveness of these resistant biotypes when compared to that of normal susceptible biotypes. If you have any information pertaining to the fitness of Group 2 (Legacy B) resistant Water Starwort from China please update the database.

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CONTRIBUTING WEED SCIENTISTS

WEITANG LIU

Shandong Agicultural University College Of Plant Protection Daizong Road 61# Tai'an 71018 Tai'an, 271018 China Email Weitang Liu

JINXIN WANG

Professor Shandong Agricultural University College Of Plant Protection Daizong Road 61# Tai'an, 271018, Shandong China Email Jinxin Wang

ACKNOWLEDGEMENTS
The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in China have been instrumental in providing you this information. Particular thanks is given to Weitang Liu, and Jinxin Wang for providing detailed information.

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Herbicide Resistant Water Starwort Globally
(Myosoton aquaticum)

Country

FirstYear

Situation

Active Ingredients

Site of Action

China

2010

Winter wheat

tribenuron-methyl

Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)

Literature about Similar Cases

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Liu, W., G. Yuan, L. Du, W. Guo, L. Li, Y. Bi, and J. Wang. . 2015. A novel Pro197Glu substitution in acetolactate synthase (ALS) confers broad-spectrum resistance across ALS inhibitors. Pesticide Biochemistry and Physiology 117 : 31 - 38.

Water chickweed (Myosoton aquaticum L.), a competitive broadleaf weed, is widespread in wheat fields in China. Tribenuron and pyroxsulam failed to control water chickweed in the same field in Qiaotian Village in 2011 and 2012, respectively. An initial tribenuron resistance confirmation test identified a resistant population (AH02). ALS gene sequencing revealed a previously unreported substitution of Glu for Pro at amino acid position 197 in resistant individuals. A purified subpopulation (WRR04) that was individually homozygous for the Pro197Glu substitution was generated and characterized in terms of its response to different classes of ALS inhibitors. A whole-plant experiment showed that the WRR04 population exhibited broad-spectrum resistance to tribenuron (SU, 318-fold), pyrithiobac sodium (PTB, > 197-fold), pyroxsulam (TP, 81-fold), florasulam (TP, > 36-fold) and imazethapyr (IMI, 11-fold). An in vitro ALS assay confirmed that the ALS from WRR04 showed high resistance to all the tested ALS inhibitors. These results established that the Pro197Glu substitution endows broad-spectrum resistance across ALS inhibitors in water chickweed. In addition, molecular markers were developed to rapidly identify the Pro197Glu mutation..

Liu WeiTang ; Bi YaLing ; Li LingXu ; Yuan GuoHui ; Du Long ; Wang JinXin. 2013. Target-site basis for resistance to acetolactate synthase inhibitor in Water chickweed (Myosoton aquaticum L.). Pesticide Biochemistry and Physiology 107 : 50 - 54.

Water chickweed is a widespread and competitive winter annual or biennial weed of wheat in China. One Water chickweed population (HN02) resistant to several acetolactate synthase (ALS) inhibitors was found in Henan province of China. Whole-plant bioassays showed that HN02 was high resistance to tribenuron (292.05-flod). In vitro ALS assays revealed that resistance was due to reduced sensitivity of the ALS enzyme to tribenuron. The I₅₀ value for HN02 was 85.53 times greater respectively than that of susceptible population (SD05). This altered ALS sensitivity in the resistant population was due to a mutation in the ALS gene resulting in a Pro197 to Ser substitution. Cross-resistance experiments indicated that HN02 exhibited various resistance patterns to pyrithiobac-sodium, florasulam and pyroxsulam, without resistance to imazethapyr. This is the first report of tribenuron-resistant Water chickweed in Henan province of China, target-site based resistance was established as being due to an insensitive form of ALS, resulting from a Pro to Ser substitution at amino acid position 197 in the ALS gene..

Liu WeiTang ; Bi YaLing ; Li LingXu ; Yuan GuoHui ; Wang JinXin. 2013. Molecular basis of resistance to tribenuron in water starwort (Myosoton aquaticum) populations from China. Weed Science 61 : 390 - 395.

Populations of water starwort, a winter annual or biennial weed in the pink family (Caryophyllaceae), can no longer be controlled by tribenuron following successive use of this herbicide over several years. Whole-plant bioassays have established that the resistant water starwort populations JS17, JS08, JS16, and JS07 showed high-level (from 203-fold to 565-fold) resistance to tribenuron. In vitro acetolactate synthase (ALS) assays revealed that resistance was due to reduced sensitivity of the ALS enzyme to tribenuron. The half-maximal inhibitory concentration (I₅₀) values for JS17, JS08, JS16, and JS07 were 72, 71, 70, and 76 times greater, respectively, than were those of the susceptible population JS24. This altered ALS sensitivity in the resistant populations was due to a mutation in the ALS gene resulting in a Pro₁₉₇ to Ser substitution (JS17, JS08, and JS16) and a Pro₁₉₇ to Leu substitution (JS07). This study established the first documented case, to our knowledge, of evolved tribenuron resistance in water starwort and concluded that the molecular basis of resistance is due, at least in part, to a target-site modification at Pro₁₉₇ in the ALS gene..

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